Thermal diffusion apparatus



April 23, 1957 J. w. THOMAS THERMAL DIFFUSION APPARATUS Filed Aug. l2,1955 Z M Z I INVENTOR. JOHN W. THoMns HTTORNE Y5 United States PatentThe Standard Oil Company, Cleveland, Ohio, a corporation of OhioApplication August 12, 1953, Serial No. 373,807

5 Claims. (Cl. 210- -176) The present invention relates to apparatus forthe separation or concentration of fluids by thermal diffusion and moreparticularly to constructions designed to compensate for the differencein thermal expansion and contraction of the wall members of suchapparatus and to facilitate their assembly.

In subjecting fluids, i. e., mixtures of materials that are gaseous orliquid under the conditions of operation 'or liquids containing one ormore components dissolved or suspended therein, to thermal diffusion forthe purpose of separating the components thereof or obtainirig fractionscontaining concentrations of one or more of the components that varyfrom those present in the original fluid, the fluid is passed through orconfined Within a thermal diffusion separation chamber defined byclosely and substantially equidistan'tly spaced surfaces, one of whichis maintained at a relatively higher temperature than the other in orderto impose a temperature gradient across the chamber. The width of thechamber, i. e., the spacing between the chamber-forming surfaces, is ofthe order of about 0.15 inch or less, preferably less than-about 0.06 or0.08 inch in apparatus designed to subjeet liquid to thermal diffusion.For the thermal diffusion of gaseous mixtures, the width of the chambermay be considerably greater but is still preferably of the order of asmall fraction of an inch.

The construction and assembly of thermal diffusion apparatus meetingthese requirements ha heretofore been attended with considerabledifliculty, particularly where the apparatus comprises a considerablenumber of fiat wall members, the exterior surfaces of which form aseries of thermal diffusion separation chamber when they are boltedtogether with gaskets disposed between them. One of these difiicultieshas been due to the fact thatwhen the apparatus is assembled, all of thewall members are at approximately room temperature, and

pansion and contraction, of the wall members promotes leakage of fluidpast the gasket or gaskets due to-differences in pressures applied tothe gaskets and to relative movement, small but appreciable in view ofthe extremely small width of the separation chamber, of the gasketcontacting portions of the wall members. In :instances where suchapparatus is assembled in the vertical position, considerable diflicultyhas also been experienced in maintaining the gaskets in their properposition until suflicient .pressure is applied thereto by adjacent wallmembers.

Similar difliculties have been encountered in the concentric tube typeof thermal diifusionapparatus. In view of the extremely small width ofthe thermal diffusion chamber, it is manifest that it is almostimpossible -to provide a cylindrical gasket'which at one and the sametime will have a sufficient wall'thickness and compressibility tofacilitate insertioninto the ends of the annular spacebetween twoconcentric tubes, and once having been inserted, exert sufficientpressure against the inner surface of the outer. tube and the outersurface of the inner tube to provide a seal that is leakproof when thetemperature conditions vary between conditions of equal temperature ofboth tubes and relatively high and low temperatures of the inner andouter tubes, respectively, or vise versa, during operation. Thisdifliculty is further aggravated by the fact that when a temperaturegradient is applied across the annular separation chamher, i. e., whenone of the tubes is heated to a temperature considerably higher than theother, the. relatively highly heated tube will expand and thus give riseto leakage of fluids in the chamber past the gasket unless the gasket isprefabricated and fitted with extreme accuracy.

The present invention is directed to constructions designed to obviatethese problems.

In accordance with the present invention, thermal diffusion apparatus isprovided which comprises two or more wall members subject todifferential thermal expansion and contraction and having closely andsubstantially equidistantly spaced surfaces that define one or morethermal diffusion separation chambers. One or more gaskets are disposedbetween and in contact with portions of the wall members to confinefluid within the chamber or chambers. The gasket-contacting portion orportions of one or more of the wall members are recessed relative to thechamber-defining surface or surfaces thereof to facilitate retention ofthe gasket or gaskets in the desired position or positions duringassembly of the apparatus and preferably also to compensate fordimensional changes in the wall member during operation and, inpreferred embodiments, make possible the use of one or more gasketshaving a thickness considerably in excess of the spacing between thechamberforming surface of the wall members.

The term recessed, as applied to a wall member herein, is intended tomeanthat the portion of the wall member referred to has an indentationin its surface which departs from the chamber-defining surface of saidwall member. Thus, for example, the recess of a wall member having aplane chamber-defining surface may be a surface portion below andparallel to, or at an obtuse angle to, the plane of the chamber-definingsurface, and the recess of a wall member having a cylindricalchamher-defining surface may be a cylindrical or conical surfaceportion, the diameter, or mean diameter, of which is greater than thediameter of said cylindrical chamberdefining surface.

Where the wall members are fiat and the chamber-defining surfaces aresubstantially parallel to one another, the gasket-contacting portion maybe recessed at an angle, preferably obtuse, to the surface thereofdefining one side of the chamber, or the recessed gasket-contactingportion of said Wall member may be substantially parallel to thechamber-defining surface. Where the gasket-contacting portion of a firstwall member is recessed at an obtuse angle, the gasket-contactingportion of the adjacent Wall member, i. e., the member having a surfacedefining the other side of the chamber, maybe parallel to the recessedgasket-contacting portion of the first wall member, or substantiallyparallel to its own chamberforming surface. Where the recessedgasket-contacting portion of the first wall member is substantiallyparallel to its chamber-forming surface, the gasket-contacting portionof the other Wall member may be similarly recessed or lie in the sameplane as the chamber-formin surface of its own wall member.

Where apparatus comprises inner and outer wall members, thechamber-defining surfaces of which are cylindrical and concentric toform an annular separation chamher, the gasket-contacting portion of theouter wall member may be provided, at one or both ends, with a conicalor cylindrical recess having a diameter greater than the diameter of itschamber-forming surface. The corresponding end or ends of the inner wallmember may be of the same diameter as the chamber-forming surfacethereof, have a radially protruding conical surface complementary to therecessed conical surface of the outer wall member, or have a radiallyprotruding cylindrical surface of lesser diameter than the diameter ofthe cylindrical recess of the outer wall member.v

The advantages and utility of the apparatus of the invention will becomefurther apparent from the following detailed description made withreference to the accompanying drawing wherein:

Figure 1 is a cross-sectional view in elevation through one preferredembodiment of the apparatus of the invention;

Figure 2 is a similar view through another preferred embodiment of theinvention;

Figures 3, 4 and 5 are fragmentary views of similar apparatus, on asomewhat larger scale, illustrating several of the alternativeembodiments of the invention;

Figure 6 is a cross-sectional view in elevation of a tubular typethermal diffusion apparatus employing the principles of the invention;and

Figures 7, 8 and 9 are fragmentary views, on a some what larger scale,illustrating several alternative embodiments of the inventionillustrated in Figure 6.

The apparatus illustrated in Figure 1 comprises two wall members It and11 having closely and substantially equidistantly spaced surfaces 12 and14 defining a thermal diffusion separation chamber 16, and a gasket 17between and in contact with the portions 19 and 20 thereof for sealingthe chamber around its periphery and maintaining the surfaces 12 and 14in spaced relation. The wall members are provided with coils 21 or othersuitable means for maintaining the surfaces 12 and 14 at differenttemperatures and one or both of the wall members are provided with ports22 for introducing the fluid into the chamber and withdrawing separatedfractions thereof.

In this embodiment the gasket-contacting portion 19 of the wall memberis at an obtuse angle (180-6) to the chamber-forming surface 12 and thegasket-contacting portion 2b of the wall member 11 is substantiallyparallel to the portion 19. The gasket 17 is substantially thicker thanthe width of the separation chamber 16. It is preferred, in thisembodiment, that the wall member 19 be the wall member that ismaintained at the relatively higher temperature during operation of thethermal diffusion separation chamber 16 inasmuch. as such a choiceinvolves a minimum possibility of leakage past the gasket 17 duringoperation or during any interruptions in operation. It is furtherpreferred that the angle 0 be an angle having a tangent equal or closeto the ratio of the chamber thickness to the chamber width. If theresiliency of the gasket is fairly large, the angle 0 may be varied overa range greater than would be possible if the gasket were not tooresilient, such as i50%.

To illustrate the manner in which this construction compensates for thedifferential expansion and contraction of the wall members 10 and 11,the contraction of the wall member 10 upon cooling from the operatingtemperature is illustrated, on an exaggerated scale, by dashed lines 24and 26 which shows an increase in chamber thickness. It will be notedthat upon contraction of the wall member 10, which shows a decrease inchamher width, the gasket-contacting portion 19 thereof will tend tocreep inwardly along the surface of the gasket 17 rather than to reducethe pressure thereon. This means that even with fluctuating temperaturesthe spacing between gasket surfaces 19 and will remain constant.

The gasket load will, therefore, remain constant, thereby assuring aleakproof seal. In addition, the recessing of the gasket-contactingportion 29 of the wall member 11 assists in maintaining the gasket 17 inthe desired position during assembly of the wall members into theposition shown.

The embodiment illustrated in Figure 2 likewise comprises wall membersltla and 11a having surfaces 12a and 14a forming a separation chamber16a and a gasket 17a. In this embodiment the wall member 11a is recessedat 26a to form a gasket-contacting portion that is substantiallyparallel to its chamber-forming surface 14a. The gasket-contactingsurface 19a of the wall member is in substantially. the same plane asits chamber-forming surface 120.

In this embodiment it is preferred that the wall member 10a be the wallmember that is maintained at a relatively higher temperature than thewall member 11a for the reason that less gasket material makes contactwith the portion 19a of the relatively hot wall member 10a than with therecessed portion 20a of the wall member 11a and is, therefore, lesssubject to deterioration by heat or to transfer of heat through thegasket to the wall member 11a. This embodiment is also preferred fromthe point of view of simplicity of the wall member 10a inasmuch as itcontains no ports, all ports 22 being in the wall member 11a.

Figure 3 illustrates an embodiment wherein both wall members 10b and 11bare recessed at the gasket-contacting portion 19b and 20b in order toaccommodate a gasket 17!) having a thickness several times the width ofthe separation chamber 16b.

In another embodiment shown in Figure 4, one wall member 11c is recessedat an angle that is obtuse to its surface forming one wall of theseparation chamber 16c, and the other wall member 100 is substantiallyplane, the gasket-contacting portion thereof being in the same planewith its chamber-forming surface 12c.

Figure 5 illustrates an embodiment similar to that of Figure 1 in whichthe spacing between the recessed gasketcontacting portion 20d of thewall member 11d and the gasket-contacting portion 19d of the wall member10d, and therefore also the operative thickness of the gasket 17d, aresubstantially equal to the width of the chamber 16d. While thisembodiment does not have the advantage !of utilizing a gasketsubstantially thicker than the width of the chamber, it possesses all ofthe thermal expansion and contraction compensating features of theembodiment illustrated in Figure 1.

Figure 6 illustrates a tubular type of thermal diffusion apparatuscomprising an inner wall member 30, an outer wall member 31, the outersurface 32 of the inner member 39 and the inner surface 34 of the outermember 31 being concentric and forming an annular separation chamber 36.The upper end of the outer member 31 is shown as having a conicallyrecessed gasket-contacting portion 37 for receiving a gasket 39, and theinner member 30 is provided, at the corresponding end, with a radiallyprotruding conical surface 4i) that is complementary to the recessedconical surface 37 of the outer member 31. At the lower end, theseparation chamber 36 is sealed by a cylindrical gasket 41 having athickness approximately equal to the width of the separation chamber 36.It is to he understood, of course, that the apparatus illustrated inFigure 6 is further provided with suitable ports, such as shown at 42,for the introduction of a fluid into the separation chamber 36 and theremoval therefrom of separated fractions, as well as with any desiredmeans for maintaining the chamber-forming surfaces 32 and 34 atdifferent temperatures to impose a temperature gradient across thechamber.

In this embodiment of the invention it will be apparent that it isnecessary to provide for relative expansion and contraction of the wallmembers 30 and 31 at only one end if the wall members are more or lessrigidly joined at the other end. It will be apparent, for example, thatif Figure 6 represents the relative positions of the various elements ofthe structure during operation, e. g., when the inner wall member 34) isrelatively hot and the outer wall member 31 is relatively cold, theinner wall member 3? will contract when the operation is interrupted orstopped and the upper end thereof will consequently tend to movedownward relative to the outer wall member 31. In the constructionillustrated in Figure 6 this will result, for the most part, in a slightsliding of the gasket-contacting portion 40 over the surface of thegasket 39 and to a minor extent in applying somewhat greater pressure tothe gasket 39. In any event, the necessity of providing a gasket of suchextremely small thickness as that of gasket 41; is avoided inasmuch asthe thickness of the gasket 39 may be several times the width of thechamber 36.

Figures 7, 8 and 9 illustrate several alternative embodinents of theinvention illustrated in Figure 6. In Figure 7 the construction of theouter wall member 310 is identi cal to that shown in Figure 6 but theinner wall member 30a has a gasket-contacting surface 40a of the samediameter as the chamber-forming surface 32a and the shape of the gasket39:: is correspondingly altered. In Figure 8 the inner wall member 3042is substantially simb lar to that illustrated in Figure 7 but the outerwall member 3115 is pr vided with a cylindrical recess 37a designed toaccommodate a cylindrical gasket 3912 having a thickness substantiallygreater than the width of the annular separation chamber 36. In order tolimit the upward movement of the gasket material 39a and 39b as a resultof the contraction of the outer tube 31, an annular ring 43 may beplaced at the top of the inner tube 30a.

In Figure 9, the outer wall member 31a is substantially similar to thatillustrated in Figure 8 and the inner wall member 30]) is provided witha radially protruding cylindrical surface having adiameter smaller thanthe diameter of the cylindrical recessed portion 37a of the outer wallmember and a gasket 390 is interposed between the portions 4% and 37a ofthe members 30]) and 31a, respectively.

It is to be understood, of course, that any two of the embodimentsillustrated in Figures 6, 7, 8 and 9 may be combined in a singleapparatus. Thus, the structures shown in Figures 7 and 8 may replace thestructure shown in the lower end of Figure 6, and the structures shownin Figures 7, 8 and 9 may replace the structure shown at the top of theapparatus in Figure 6.

It is further to be understood that innumerable modifications will atonce become apparent to those skilled in the art upon reading thisdescription. All such modifications are intended to be included withinthe scope of the invention as defined in the appended claims.

I claim:

1. Thermal diffusion apparatus comprising two wall members subject todifferential thermal expansion and contraction and having closely andsubstantially equidistantly spaced surfaces defining a thermal diffusionseparation chamber, means associated with each of said wall members formaintaining one of said surfaces at a higher temperature than'the otherto maintain a temperature gradient across said chamber, and a gaskethaving a portion thicker than the spacing between said surfaces andbeing positioned between and in contact with portions of said wallmembers for confining fluid within said chamber, the gasket-contactingportion of one of the wall members having a recess in itschamber-defining surface to admit said gasket, the gasket contactingportion of said other of the wall members being aligned with the chamberdefining surface of said other of the wall members.

2. The apparatus defined in claim 1 wherein the wall members andchamber-defining wall surfaces are cylindrical and concentric and forman annular separation chamber.

3. The apparatus defined in claim 2 wherein one end of the outer wallmember having an inner cylindrical surface defining one side of theannular separation chamber is provided with a cylindrical recess ofgreater diameter than the diameter of said inner cylindrical surface,said outer wall member adapted to be maintained at a relatively lowertemperature than the inner wall member, the gasket-contacting portion ofthe inner wall member being a cylindrical surface coaxial with thechamberclefining wall surface of the inner wall member.

4. The apparatus defined in claim 2 wherein one end of the outer wallmember having an inner cylindrical surface defining one side of theannular separation chamber is provided with a cylindrical recess ofgreater diameter than the diameter of said inner cylindricm surface andthe corresponding end of the inner wall member having an outercylindrical surface defining the other side of the annular separationchamber has a diameter substantially equal to the diameter of said outercylindrical surface, said outer wall member adapted to be maintained ata relatively lower temperature than said inner wall member, thegasket-contacting portion of the inner wall member being a cylindricalsurface coaxial with said outer cylindrical surface of said inner wallmember.

5. The apparatus defined in claim 2 wherein one end of the outer wallmember having an inner cylindrical surface defining one side of theannular separation chamber is provided with a cylindrical recess ofgreater diameter than the diameter of said inner cylindrical surface andthe corresponding end of the inner wall member having an outercylindrical surface defining the other side of the annular separationchamber is provided with a radially'protruding cylindrical surfacehaving a diameter smaller than the diameter of the cylindricallyrecessed portion of the outer wall member, said outer wall memberadapted to be maintained at a relatively lower temperature than saidinner wall member, the gasket-contacting portion of the inner wallmember being a cylindrical surface coaxial with said outer cylindricalsurface of the inner wall member.

References Cited in the file of this patent UNITED STATES PATENTS DebyeSept. 11, 1951

1. THERMAL DIFFUSION APPARATUS COMPRISING TWO WALL MEMBERS SUBJECT TODIFFERENTIAL THERMAL EXPANSION AND CONTRACTION AND HAVING CLOSELY ANDSUBSTANTIALLY EQUIDISTANTLY SPACED SURFACES DEFINING A THERMAL DIFFUSIONSEPARATION CHAMBER, MEANS ASSOCIATED WITH EACH OF SAID WALL MEMBERRS FORMAINTAINING ONE OF SAID SURFACES AT A HIGHER TEMPERATURE THAN THE OTHERTO MAINTAIN A TEMPERATURE GRADIENT ACROSS SAID CHAMBER, AND A GASKETHAVING A PORTION THICKER THAN THE SPACING BETWEEN SAID SURFACES ANDBEING POSITIONED BETWEEN AND IN CONTACT WITH PORTIONS OF SAID WALLMEMBERS FOR CONFINING FLUID WITHIN SAID CHAMBER, THE GASKET-CONTACTINGPORTION OF ONE OF THE WALL MEMBERS HAVING A RECESS IN ITSCHAMBER-DEFINING SURFACE TO ADMIT SAID GASKET, THE GASKET CONTACTINGPORTION OF SAID OTHER OF THE WALL MEMBER BEING ALIGNED WITH THE CHAMBERDEFINING SURFACE OF SAID OTHER OF THE WALL MEMBERS.